You shouldn't have given up so quickly. I am not surprised that your bread was too sour when you leave it to prove fo 30 hours. - I have been baking sourdough bread for 8 years now because I was fed up with the so-called bread from the local supermarkets; there are no independent bakeries where I live. I have even stopped bringing back bread from trips to Germany. - I leave my bread to prove up to 24 hours, sometimes only for 16 hours. The shorter proving times will result in a milder less sour bread. You could also add some wheat flour instead of baking a plain rye bread. To have some variety I also like to bake wheat bread with a wheat sourdough.

TomUK